def makeNeighbors():
    # Open the file
    f = open("words.dat", "r")
    
    # Read the words into the "master" wordList
    masterWordList = []
    for line in f:
        masterWordList.append(line.rstrip())
    
    # From the master wordList, generate 5 word dictionaries, each containing all 4-letter words
    # obtained by removing the letter in a particular position of all the words. In other words,
    # shortWordDicts[0] contains all words in masterWordList with the first letter removed, as 
    # dictionary keys, with the removed letters appearing as a list of corresponding values.
    shortWordDicts = [{}, {}, {}, {}, {}]
    for i in range(5):
        for x in masterWordList:
            shortWord = x[0:i]+x[i+1:5]
            letter = x[i]
            if shortWord not in shortWordDicts[i]:
                shortWordDicts[i][shortWord] = [letter]
            else:
                shortWordDicts[i][shortWord].append(letter)

    # Prepare a dictionary that will eventually keep track of the word-neighbors
    # Initially all neighborlists are empty
    wordDict = {}
    for word in masterWordList:
        wordDict[word] = []
        
    # Process each word in the master list
    for word in masterWordList:   
        for i in range(5):
            shortWord = word[0:i] + word[i+1:5] # Create a 4-letter word for it by removing a letter in the ith position
            missingLetters = shortWordDicts[i][shortWord] # Look in the appropriate 4-letter word list to find matches
            wordDict[word].extend([word[0:i] + letter + word[i+1:5] for letter in missingLetters])
            wordDict[word].remove(word) # a word should not be in its own set of neighbors
            
    return wordDict